The invention relates to a power-driven hand tool, comprising a tool spindle that can be driven in a rotational oscillatory manner about its longitudinal axis and that is designed to carry a tool, and comprising a transmission housing, in which there is carried an eccentric coupling drive for driving the tool spindle and from which the tool spindle projects outwardly with one end.
Such a hand tool is known from WO 2008/128804 A1. The tool in that case is a power tool having a drive unit, for driving a drive shaft, and having an output shaft, on which a tool is carried. The rotary motion of the drive shaft can be transferred to the output shaft via an eccentric coupling device.
Such hand tools provided with an oscillatory drive can be used, for instance, to cut or grind workpieces, the oscillatory motion of the tool making it possible, in principle, to achieve precise guidance with a high cutting and material removal rate.
It has been found that, during use of such hand power tools, vibrations can occur that a user may perceive as irritating in the case of prolonged use.
In this connection, for the purpose of vibration compensation, WO 2008/128804 A1 proposes a mass compensation device, which executes a compensatory motion counteracting the oscillatory motion generated by the oscillatory drive.
In principle, therefore, it is possible to reduce vibrations, but the mass compensation device necessitates a more elaborate structure and a considerable additional weight. In addition, the mass compensation device requires a whole series of parts that are movably coupled to one another and that have to be supplied with transmission grease in order to ensure that the machine runs smoothly. Since the oscillatory drive concerned is usually operated at high frequency, this results in flexing motions and grease stresses being produced, which can result in heating of the tool and which can have a detrimental effect upon the efficiency and service life of the machine concerned.